Method for transmitting data in a blood glucose system and corresponding blood glucose system

ABSTRACT

A method for wireless transmission of data between a master controller ( 2, 2 ′) having a receiver ( 10 ) and a transmitter ( 9 ), and at least one slave device ( 3 ) having a receiver ( 19 ) and a transmitter ( 18 ), and to a corresponding blood glucose system ( 1 , I 1 ). The slave device ( 3 ) is normally operated in a power saving mode in which its receiver ( 19 ) is only activated intermittently at a receiver activation frequency for a predetermined listening period. The controller ( 2, 21 ) transmits a communication initiation data frame to the slave device ( 3 ) by means of a signal comprising a preamble signal transmitted for a preamble period. Upon receipt of the communication initiation data frame, the slave device ( 3 ) is switched to a communication mode in which it transmits a response to the controller ( 2, 21 ), and the slave device ( 3 ) is switched from the communication mode to the power saving mode.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.12/297,621 filed Apr. 20, 2006, now allowed (to be granted as U.S. Pat.No. 8,099,074) and which claims priority from International Applicationnumber PCT/EP2006/003650, filed Apr. 20, 2006, to which applicant claimsthe benefits of priority under 35 USC §119, 120, or 365, and which bothapplications are fully incorporated herein by reference.

DESCRIPTION

The present invention relates to a method for wireless transmission ofdata between components of a blood glucose system including a mastercontroller and a slave device comprising an insulin dispensing means,and to a corresponding blood glucose system.

Diabetes mellitus is a chronic metabolic disorder caused by an inabilityof the pancreas to produce sufficient amounts of the hormone insulin sothat the metabolism is unable to provide for the proper absorption ofsugar and starch. This failure leads to hyperglycemia, i.e. the presenceof an excessive amount of glucose within the blood plasma. Persistenthyperglycemia causes a variety of serious symptoms and life threateninglong term complications such as dehydration, ketoacidosis, diabeticcoma, cardiovascular diseases, chronic renal failure, retinal damage andnerve damages with the risk of amputation of extremities. Becausehealing is not yet possible, a permanent therapy is necessary whichprovides constant glycemic control in order to always maintain the levelof blood glucose within normal limits. Such glycemic control is achievedby regularly supplying external insulin to the body of the patient tothereby reduce the elevated levels of blood glucose.

External insulin was commonly administered by means of typically one ortwo injections of a mixture of rapid and intermediate acting insulin perday via a hypodermic syringe. While this treatment does not require thefrequent estimation of blood glucose, it has been found that the degreeof glycemic control achievable in this way is suboptimal because thedelivery is unlike physiological insulin production, according to whichinsulin enters the bloodstream at a lower rate and over a more extendedperiod of time. Improved glycemic control may be achieved by theso-called intensive insulinotherapy which is based on multiple dailyinjections, including one or two injections per day of long actinginsulin for providing basal insulin and additional injections of rapidlyacting insulin before each meal in an amount proportional to the size ofthe meal. Although traditional syringes have at least partly beenreplaced by insulin pens, the frequent injections are nevertheless veryinconvenient for the patient.

Substantial improvements in diabetes therapy have been achieved by thedevelopment of blood glucose systems relieving the patient of the dailyuse of syringes or insulin pens. Such blood glucose systems usuallycomprise a battery-operated insulin pump and a separate battery-operatedcontrol unit. The insulin pump allows for the delivery of insulin in amore physiological manner and can be controlled to follow standard orindividually modified protocols to give the patient a better glycemiccontrol over the course of a day. It can be constructed as animplantable device for subcutaneous arrangement or can be constructed asan external device that is carried on the body of the patient.

The operation of the insulin pump can be controlled and modified bymeans of the control unit. For example, delivery of suitable amounts ofinsulin by the insulin pump requires that the patient frequentlydetermines his or her blood glucose level and inputs this value into thecontrol unit, which then calculates a suitable modification to thedefault or currently in use insulin delivery protocol, i.e. dosage andtiming, and subsequently communicates with the insulin pump to adjustits operation accordingly. The determination of blood glucoseconcentration is performed by means of a suitable battery-operatedmeasuring device such as a hand-held electronic meter which receiveblood samples via enzyme-based test strips and calculates the bloodglucose value based on the enzymatic reaction. Advantageously, themeasuring device is an integral part of the blood glucose system, sothat the measured value is automatically delivered to the control unit.In this regard, the measuring device may be integrated into the housingof the control unit or may be provided as a separate devicecommunicating with the control unit. Further, it may be necessary to usethe control unit each time the patient eats to instruct the pump toadminister a specified amount of insulin to cover that meal. Recently, amore or less closed-loop control has been realized in which the controlunit modifies the insulin delivery protocol automatically.

In view of the permanence of the therapy, it is desirable to provide thediabetic patient with flexibility, convenience and ease of use in orderto increase the quality of his or her life. In this regard, it isevident that cable connections between the individual devices of a bloodglucose system are disadvantageous. Thus, it is known to provide awireless communication link. However, when implementing wirelesscommunication, it has to be taken into account that the necessaryreceivers and transmitters are a main source of energy consumption.Thus, their use results in reduced battery life and necessitates a morefrequent replacement or recharge of the batteries of the individualdevices. In medical devices, this issue is not only inconvenient to thepatient but also increases the danger of the devices not workingproperly when needed. Further, for implantable devices the replacementor recharge of the battery is accompanied by surgery. Therefore, it isimportant to provide for an efficient usage of the transmitters andreceivers.

One possibility to reduce the energy consumption is the reduction oftransmitting power. However, in many applications this is notsufficient. Therefore, the receivers and transmitters are commonly onlyactivated regularly from time to time during distinct spaced listeningand transmission periods, and synchronization means are provided whichseek to maintain coincidence between the listening and transmissionperiods. With regard to battery life, it is desirable to reduce theduration of the individual listening and transmission periods and toincrease the spacing between each two successive periods. Due to thespaced listening periods, it is, however, no longer possible to transmita message immediately upon request. Rather, a device wishing to transmita message to a particular recipient has to wait at least until the startof the next listening period of the recipient, and has further to waitfor a confirmation of receipt at least until its own subsequentlistening interval. Therefore, extended periods during which thereceivers are deactivated have the disadvantage that they tend to resultin substantial delay times which are inconvenient to the patient. Thus,there is a lower limit below which the spacing between successivelistening periods should not fall if a suitable compromise betweenbattery life and delay time is to be achieved.

One exemplary blood glucose system operating in this way is described inU.S. Pat. No. 6,585,644. This reference discloses a battery-operatedexternal communication device that wirelessly communicates with at leastone battery-operated medical device such as an implantable insulin pumpand/or a blood glucose sensor via telemetry messages. The correspondingcommunication protocol is designed for low power consumption, inparticular of the medical device(s), as well as for low communicationdelay times. According to the protocol, in all devices the receiver isactivated only during distinct listening periods separated by periods ofinactivity. The length of the listening periods determines the energyconsumption, and the spacing between successive listening periodsdetermines the delay time. The telemetry messages include a preambleportion which effects the transmission of a preamble signal upontransmission of the message. Transmission of telemetry messages occursin corresponding transmission periods between which the transmitter isdeactivated. The devices seek to stay synchronized with respect to eachother such that the transmission and listening periods coincide. In caseof failure of communication or loss of synchronization, the transmissionperiods may be extended or shifted, or the preamble signal may betransmitted over an extended period of time in order to catch alistening period of the target device. The implantable medical devicemay have a storage mode to which it can be shifted during periods ofnon-use and in which the spacing between successive listening periods issubstantially increased to conserve battery power. This system has thedisadvantages indicated above. It is still desirable to decrease thedelay time further without substantially increasing energy consumption.

U.S. Pat. No. 6,807,159 discloses a protocol designed to reduce powerconsumption in master driven wireless networks without substantiallyincreasing the delay time. The master regularly transmits a pollingmessage to the slave devices which only activate their receiver duringthe transmission of this message. For each slave device, a probabilitybased approach is used in order to predict the arrival time of the nextdata packet. The result of this prediction is then used to adjust thepolling interval for each slave device. This adaptive probability basedpolling interval mechanism can lead to an optimization with respect tobattery life and delay time if the time distribution of the traffic ateach device is approximately constant. However, the mechanism cannot beapplied advantageously to wireless blood glucose systems in whichcommunication between the controller and the other devices of the systemtakes place only from time to time, so that the traffic distribution ishighly non-uniform.

It is the object of the present invention to provide a method forwireless transmission of data between components of a blood glucosesystem that combines a low power consumption of all components of thesystem with low delay times and that remedies the disadvantages found inthe prior art, and to provide a corresponding blood glucose system.

This object is achieved by a method with the features of claim 1 and bya blood glucose system with the features of claim 13. Further preferredembodiments of the invention are the subject-matter of the respectivedependent claims.

The steps of the method of the present invention are performed by thecomponents of a blood glucose system that includes an insulin dispensingdevice and a separate remote controller in order to wirelessly transfercommands, statuses and other data between the individual devices of thesystem. The data stream between the devices follows themaster-slave-principle, wherein the remote controller is the master andthe insulin dispensing device and possible further devices are slaveswhich in the usual manner never initiate a communication but onlyrespond to messages received from the remote controller, i.e. only themaster has the right to initiate a communication cycle, whereas theslave devices only transmit when requested by the master to ensure thattwo slave devices can never occupy the air interface at the same time.Each of the devices of the blood glucose system includes a receiver anda transmitter for wireless receipt and transmission, respectively, ofmessages.

The insulin dispensing device normally operates in a power saving modein which its receiver is activated intermittently at a receiveractivation frequency, with the receiver each time being activated for apredetermined listening period and the receiver being deactivated forthe rest of the time. In a preferred embodiment, the predeterminedlistening period can e.g. be 10 ms. In case it is intended to use thecontroller to transmit data to the insulin dispensing device or torequest a response from the insulin dispensing device, the transmitterof the controller is activated for a transmission period to transmit asuitable data frame addressed to or intended for the insulin dispensingdevice. Obviously, apart from the cases in which the blood glucosesystem does not include a further slave device in addition to theinsulin dispensing device or in which it is intended to transmit thedata frame to all slave devices of the blood glucose system, the dataframe preferably includes an indication that the data frame is addressedto the insulin dispensing device. The data frame includes a preambleportion which is adapted such that upon transmission of the data frame apreamble signal is transmitted for a preamble period. All or some of thedata frames may be communication initiation data frames. This type ofdata frame is transmitted by the controller if it wishes to establishcommunication with the insulin dispensing device. Following transmissionof the communication initiation data frame, the transmitter of thecontroller is deactivated, and then the receiver of the controller isactivated for a response period. In a preferred embodiment, the responseperiod can e.g. be 50 ms to 500 ms and preferably about 100 ms. In anycase, the chosen response period must sufficiently exceed the commandprocessing times of the slave devices and must be sufficiently short tomeet the desired performance and responsiveness requirements. In casethe slave device receives the preamble signal, i.e. at least a part ofthe preamble included in the preamble portion of the communicationinitiation data frame, during a listening period, the receiver of theinsulin dispensing device is maintained active until at least a portionof the remainder of the communication initiation data frame has beenreceived by the insulin dispensing device. Following receipt of acommunication initiation data frame addressed to or intended for theinsulin dispensing device, the insulin dispensing device is switchedinto a communication mode in which its transmitter is activated totransmit a response to the controller. This response is likewiseconstituted by a data frame and, depending on the type of data frametransmitted by the controller, may be a mere confirmation of receipt ormay include further data requested by the controller. The responsetransmitted by the insulin dispensing device following receipt of acommunication initiation data frame indicates to the controller that theinsulin dispensing device indeed received the communication initiationdata frame and switched to communication mode. Subsequently or in afurther step, the insulin dispensing device is switched back from thecommunication mode to the power saving mode.

According to the invention, upon switching back from communication modeto power saving mode the receiver activation frequency is initially setto a first frequency value. If no communication initiation data frame isreceived by the insulin dispensing device during a predetermined powersaving timeout period, the receiver activation frequency is set to asecond frequency value smaller than the first frequency value, therebyproviding a “high frequency” power saving mode and a “low frequency”power saving mode. On the other hand, if a communication initiation dataframe has been received, the insulin dispensing device is switched tocommunication mode as described above. Thus, every time the insulindispensing device has received a communication initiation data frame andcommunicated with the controller, the spacing between successivelistening periods is initially chosen such that a very low delay timebut a slightly higher energy consumption than usual results. Only aftersome time without a further communication initiation data frameaddressed to or intended for the insulin dispensing device from thecontroller, the spacing between successive listening periods is chosensuch that the delay time is increased and the energy consumption isdecreased to its usual power saving value. This two-step process isadvantageous for a blood glucose system, because the patient usuallyonly uses the controller a few times a day (and overall communicationbetween the controller and the insulin dispensing device only occursfrom time to time), and only during such times, a high delay time isexperienced as inconvenient.

It has been realized that most uses of the controller involve aplurality of messages being sent from the controller to the insulindispensing device within a small period of time, i.e. the communicationbehavior is highly non-uniform. According to the method of the presentinvention, the delay time is reduced at each possible beginning of suchan interval of high traffic.

In the communication initiation data frames transmitted by thecontroller, the length of the preamble portion is chosen such that thepreamble period exceeds the length of the cycle duration correspondingto the first frequency value. If no response is received during theresponse period, i.e. in case the insulin dispensing device hasapparently not received the preamble signal in one of its listeningperiods, the length of the preamble portion is increased such that thepreamble period exceeds the length of the cycle duration correspondingto the second frequency value, and the communication initiation dataframe is retransmitted with this modified preamble portion. Thus, thecontroller initially transmits the communication initiation data framesuch that it is only received if the insulin dispensing device is in the“high frequency” power saving mode or if one of its listening periodshappens to overlap with the transmission time of the preamble signal. Ifthe communication initiation data frame is received by the insulindispensing device, energy is saved because the communication initiationdata frame is transmitted with a short preamble period. Only if thiscommunication attempt is not successful, the communication initiationdata frame is transmitted such that it is definitely received at theinsulin dispensing device operating in the “low frequency” power savingmode.

The method of the present invention provides the advantage that for theparticular non-uniform traffic pattern of a blood glucose system, a lowenergy consumption at both the remote controller and the insulindispensing device is combined with a low response time of the insulindispensing device to requests transmitted by the controller.

The method of the present invention can be advantageously applied incase the blood glucose system includes, in addition to the insulindispensing device, a blood glucose sensing device which is likewiseconfigured as a slave device, and/or possibly one or more otheradditional slave devices. All slave devices of such a system, i.e. theinsulin dispensing device, the blood glucose sensing device and possiblyother slave devices, perform the same steps as described above for theinsulin dispensing device. Accordingly, with respect to wirelesscommunication, the slave devices show an identical behavior, i.e. followthe same communication protocol.

In the case of a blood glucose system comprising more than one slavedevice, the controller may transmit data to a particular slave device orrequest a response from a particular slave device as described above forthe insulin dispensing device, i.e. by activating the transmitter of thecontroller for a transmission period to transmit a suitable data frameaddressed to this slave device. It is then preferred to include anindication of the target slave device for which the communicationinitiation data frame is intended in the communication initiation dataframe transmitted by the controller in order to establish communicationwith the slave device. Upon receipt of the preamble signal by a slavedevice during one of its listening periods, its receiver is maintainedactive until the target device indication included in the communicationinitiation data frame has been received. At this point, it can bedetermined whether the communication initiation data frame is addressedto this slave device. Only if the communication initiation data frame isindeed addressed to this slave device, its receiver is maintained activeuntil the remainder of the communication initiation data frame has beenreceived and the slave device is switched into communication mode asdescribed above. Otherwise, the slave device is maintained in the powersaving mode. However, the activation frequency for the slave device ischanged to a third frequency value greater than the second frequencyvalue, and only if no communication initiation data frame is receivedfor a predetermined timeout period, which may e.g. be identical to theabove predetermined power saving timeout period, the activationfrequency is changed back to the second frequency value. Thus, whenevera communication initiation data frame is received, a slave devicereduces the delay time even if the communication initiation data frameis addressed to another slave device. This behavior is advantageousbecause it has been found that during any period of high traffic thecontroller will most likely not only communicate with one slave devicebut with all slave devices in turn. Preferably, the third frequencyvalue and the first frequency value are chosen to be identical.

In a preferred embodiment, the first frequency value is chosen such thatthe receiver of the insulin dispensing device is activated every 100 to500 ms, preferably every 300 ms, and the second frequency value ischosen such that the receiver of the insulin dispensing device isactivated every 0.5 to 30 s, preferably every 2 to 20 s and mostpreferably about every 3 s. In this regard, it is advantageous if theactivation period corresponding to the second frequency value is anintegral multiple of the activation period corresponding to the firstfrequency value. It is evident that the frequency values are always acompromise between suitable response times and sufficiently low energyconsumption and have to be chosen to meet the particular requirements.

On the one hand, higher frequency values increase the energy consumptionof the slave devices, but reduce the energy consumption of thecontroller because shorter preamble periods may be utilized. On theother hand, lower frequency values reduce the energy consumption of theslave devices, but result in longer delay times and, due to longerpreamble periods being necessary, in an increased energy consumption ofthe controller. Further, the short and the long preamble periodsutilized by the controller are preferably chosen such that they exceedthe time period of the “high frequency” power saving mode and the “lowfrequency” power saving mode, respectively, by about 25 ms. Thus, in themost preferred embodiment, the preamble periods are approximately 325 msand approximately 3025 ms, respectively. Further, it is preferred thatthe predetermined power saving timeout period is 10 s to 60 s andpreferably about 15 s. The optimum value of the predetermined powersaving timeout period for a particular application should be chosen onthe one hand based on an estimation of the average time period betweendifferent user actions on the controller that require wirelesscommunication, and on the other hand on an estimation of the time afterwhich the user may be considered not to seek to invoke another userinteraction requiring wireless communication. The above values for thevarious parameters result in a good balance between low energyconsumption and low response time of the blood glucose system.

In the case of more than one slave device, it may be advantageous insome instances if the above method is modified such that, upon switchingof a slave device from communication mode to power saving mode, thereceiver activation frequency is immediately set to the second frequencyvalue without first setting it to the first frequency value. Thismodified method can be advantageous if in all probability the controllerpolls each slave device exactly once during each communication period.In such a case, an additional power saving can be achieved on the sideof the slave devices.

The method may involve that all data frames transmitted by thecontroller are communication initiation data frames. However, it ispreferred that following transmission of a communication initiation dataframe the controller also sends further data frames. Thus, in apreferred version of the method of the present invention, followingtransmission of a communication initiation data frame, the transmitterof the controller is activated for at least one further transmissionperiod to transmit at least one further data frame addressed to orintended for the same slave device and including a preamble portionwhich is chosen such that the preamble signal is transmitted for apreamble period, and following transmission of each of the least onefurther data frame the receiver of the controller is activated for aresponse period, which in a preferred embodiment can be e.g. 50 ms to500 ms, preferably about 100 ms. In order to provide a possibility forthe slave devices to distinguish communication initiation data framesfrom further data frames and possibly to distinguish between differenttypes of further data frames, all data frames transmitted by thecontroller include a command portion in which a command is included thatidentifies the content of the data frame. For any communicationinitiation data frame, a communication initiation command is included inthe respective command portion to identify this data frame as acommunication initiation data frame.

In case a slave device receives the preamble signal during a listeningperiod while it is in the power saving mode, the receiver of the slavedevice is maintained active at least until the command included in thecommand portion of the data frame has been received, and the slavedevice is maintained in the power saving mode in case the command is notthe communication initiation command. On the other hand, in case a slavedevice receives the preamble signal while it is in the communicationmode, the receiver of the slave device is maintained active at leastuntil the command included in the command portion of the data frame hasbeen received. If the command is not the communication initiationcommand and the slave device is the intended recipient of the dataframe, the receiver of the slave device is maintained active until theremainder of the data frame has been received, and then the transmitterof the slave device is activated and deactivated to transmit a responseto the controller. Thus, the slave devices only respond to further dataframes if they are already in communication mode. It should be notedthat each slave device transmits a response upon receipt of thecommunication initiation data frame instructing this slave device toswitch to communication mode, i.e. the communication initiation dataframe starting a communication cycle, as well as upon receipt of anyfurther data frame addressed to this slave device and received by thisslave device when it is still in communication mode. Therefore, in eachcommunication cycle with a particular slave device, all data framestransmitted by the controller to this slave device entail a responsedata frame transmitted by the slave device to the controller. Dependingon the type of data frame transmitted by the controller, the responsedata frame may be a mere confirmation of receipt or may include furtherdata requested by the controller.

In a preferred embodiment, the communication mode at a particular slavedevice is terminated if no communication initiation data frame orfurther data frame addressed to this slave device is received for apredetermined communication timeout period, and the communication modeis arranged such that the receiver of the respective slave device ismaintained active whenever its transmitter is not activated to transmita response. Thus, starting with the receipt of the communicationinitiation data frame a particular slave device is maintained incommunication mode at least for the predetermined communication timeoutperiod. In communication mode, the delay time is substantially zero asthe receiver of the slave device is active all the time, so thatefficient communication involving a plurality of further data frames andcorresponding responses is achieved. In this way, a number of dataframes can be transmitted to the slave device with substantially zerodelay time. It is further preferred that at the controller the timesince transmitting the last data frame to a particular slave device istracked and that it is determined at the controller, prior totransmitting a further data frame to the same slave device, based on acomparison between the measured time and the predetermined communicationtimeout period whether this slave device is expected to still be incommunication mode. If it is determined that the slave device isexpected to still be in communication mode, the controller initiallytransmits the data frame such that the preamble period spans a timeperiod shorter than the cycle durations corresponding to the firstfrequency value and the second frequency value. In fact, the preambleperiod can be chosen to have a minimum duration, such as e.g. about 25ms, because in communication mode the receiver of the slave device isalways activated. In this way, additional energy saving is achieved onthe side of the controller. In a preferred embodiment, the predeterminedcommunication timeout period is 0.2 to 2.5 s and preferablyapproximately 2 s.

In the case of such an extended communication mode, it is furtherpreferred to provide the option of including a delay time periodindication into a response transmitted by a slave device to a particularfirst data frame to indicate that the actual response will betransmitted later. With other words, in case a slave device determinesthat it cannot transmit a response within the response period followingtransmission of the data frame, it can indicate to the controller thatthere will be a delay in the response. Then the transmitter and thereceiver of both the slave device and the controller are deactivated forthe indicated delay time period. Only after the end of the indicateddelay time period, the transmitter of the controller and the receiver ofthe slave device are activated, so that the controller may transmit asecond data frame requesting the delayed response from the slave deviceand the slave device can receive this request. Upon receipt of therequest data frame, the transmitter of the slave device is activated totransmit the requested response to the controller. In this way, theresponse period can be chosen to be relatively small in order to saveenergy.

In the case of such an extended communication mode in which acommunication cycle involves a communication initiation data framefollowed by one or more additional data frames, it is advantageous ifthe data frames transmitted by the controller and by the slave device(s)include a frame number or frame reference uniquely identifying the dataframe within a particular communication cycle. For example, thecommunication initiation data frame may include the frame number 1, andthe data frame transmitted by the addressed slave device in response tothe communication initiation data frame may likewise include the framenumber 1. For each additional data frame transmitted by the controllerand the corresponding response data frame the frame number is increasedby 1, i.e. the first additional data frame and the response data framehave the frame number 2, the second additional data frame and theresponse data frame have the frame number 3 on so on. In anotherexample, the communication initiation data frame includes the framenumber 1, the data frame transmitted by the addressed slave device inresponse to the communication initiation data frame includes the framenumber 2, the first additional data frame transmitted by the controllerincludes the frame number 3, and so on. In any case, by means of suchframe numbers or frame references it can be guaranteed that all commandsissued by the controller by means of transmitting corresponding dataframes are executed exactly once by the addressed slave device in apredetermined order. The controller knows which frame number or framereference a response data frame confirming execution of a command musthave, so that the controller may reissue the command until execution ofthe command is confirmed. Further, the slave device knows which framenumber or frame reference the additional data frame corresponding to thenext command in a sequence of commands must have, so that it may issue awarning in case a command in the sequence is missing, and so thatexecuting a particular command more than once is prevented.

In order to further increase the safety of the blood glucose system, itis also advantageous if each data frame not only includes an indicationof the addressed slave device (in case of more than one slave device),but also a source device reference uniquely identifying the device(controller or slave device) that transmitted the data frame. Thissource device reference may be utilized to ensure that the components ofa particular blood glucose system disregard data frames not belonging tothis blood glucose system.

In a further preferred embodiment, the controller may transmit a dataframe including a termination command to a slave device in communicationmode, and the slave device terminates the communication mode uponreceipt of this termination data frame. Thus, in case it is not intendedto use the controller to transmit a further data frame to a slave devicein communication mode, the communication mode involving a substantiallypermanently activated receiver may be terminated prior to the end of thecommunication timeout period in order to save energy. This possibilityof terminating the communication mode of a slave device is preferablycombined with the above described embodiment in which the communicationmode at a particular slave device is terminated if no communicationinitiation data frame or further data frame addressed to this slavedevice is received for a predetermined communication timeout period. Itis then preferred that the communication mode should always beterminated by means of a termination command, and that the communicationtimeout period is only provided as a safety feature to avoid that incase of errors a slave device inadvertently remains in communicationmode permanently.

It is further preferred that the transmission of at least onecommunication initiation data frame by the controller is initiated byuser request, i.e. the communication initiation data frame istransmitted without waiting for some predetermined transmission window.This may be the case if the patient decides to modify the insulindelivery protocol or to change some other setting of a slave device, orif the patient needs to dispense insulin prior to a meal.

Additionally or alternatively, it is preferred that a timer event isperiodically generated in the controller and that a communicationinitiation data frame is transmitted by the controller upon eachoccurrence of such a timer event. In this regard, it is particularlyadvantageous to choose the frequency at which the timer events occur tohave the second frequency value or such that the second frequency valueis an integral multiple of the timer event frequency, to include a timereference in each communication initiation data frame initiated by atimer event, to examine the time reference upon receipt at a slavedevice, and to synchronize, based on the time reference, the start timesof the listening periods of the slave devices with the timer events. Inthis way, irrespective of the current activation frequency value of atarget slave device, it is ensured that the controller can reach thetarget slave device using a preamble period that only needs to exceedthe length of the cycle duration corresponding to the first frequencyvalue. Thus, energy consumption as well as delay time are reduced. Thetimer event triggered transmission of a communication initiation dataframe or autopolling is utilized e.g. for automatic control andmaintenance of the slave devices. Thus, timer event generatedcommunication cycles may serve to periodically check the status of theslave devices or to control the operation of the slave devices, e.g. toregularly dispense suitable amounts of insulin by means of the insulindispensing device. Preferably, such timer events are generated every 3to 5 min, preferably about every 5 min. Further, it may be advantageousif the communication initiation data frames transmitted upon occurrenceof a timer event are distinguished from communication initiation dataframes initiated by user request, and if the slave device receiving acommunication initiation data frame determines whether the communicationinitiation data frame was initiated by a timer event or by user request.In this way, the communication timeout period, the power saving timeoutperiod and/or the timeout period utilized by slave devices not addressedby a communication initiation data frame to determine when to changefrom “high frequency” power saving mode to “low frequency” power savingmode may be chosen to be shorter for a communication initiation dataframe initiated by a timer event than for a communication initiationdata frame initiated by user request. This can be advantageous, becausein most instances autopolling does not require extended communicationand because autopolling does not require user interaction so thatextended delay times do not lead to user annoyance.

The present invention further relates to a blood glucose systemimplementing the method of the present invention. Such a systemcomprises a master controller having a receiver, a transmitter and acontrol means, wherein the control means is operable to activate thetransmitter for a transmission period in order to transmit acommunication initiation data frame including a preamble portion suchthat a preamble signal is transmitted for a preamble period, and tosubsequently activate the receiver for a response period. The systemfurther includes a slave device comprising an insulin dispensing meansand having a receiver, a transmitter and a control means, wherein theslave device is adapted to be worn on or to be implanted subcutaneouslyinto the body of a patient such that insulin can be delivered from theslave device to the body of the patient. The control means of the slavedevice is adapted to operate the slave device normally in a power savingmode in which the control means activates the receiver intermittently ata receiver activation frequency, with the receiver each time beingactivated for a predetermined listening period of e.g. 10 ms and thereceiver being deactivated for the rest of the time. The control meansof the slave device is further adapted to determine whether the receiverof the slave device receives the preamble signal of the communicationinitiation data frame during a listening period, and in case thepreamble signal is received to maintain the receiver of the slave deviceactive until at least a portion of the remainder of the communicationinitiation data frame has been received, switch the slave device to acommunication mode in which the control means activates the transmitterof the slave device to transmit a response to the controller, andsubsequently switch the slave device from the communication mode to thepower saving mode. The response transmitted by the insulin dispensingdevice following receipt of a communication initiation data frameindicates to the controller that the insulin dispensing device indeedreceived the communication initiation data frame and switched tocommunication mode.

According to the present invention the control means of the slave deviceis adapted to initially set the activation frequency to a firstfrequency value upon switching the slave device from communication modeto power saving mode, and to set the activation frequency to a secondfrequency value smaller than the first frequency value if the receiverdoes not receive a communication initiation data frame intended for theslave device for a predetermined power saving timeout period, whereinthe control means of the controller is adapted to transmit thecommunication initiation data frame such that the preamble periodexceeds the length of the cycle duration corresponding to the firstfrequency value, and, in case no response is received during theresponse period, to adapt and retransmit the communication initiationdata frame such that the preamble period is increased and exceeds thelength of the cycle duration corresponding to the second frequencyvalue.

In a preferred embodiment, the first frequency value is chosen such thatthe receiver of the slave device is activated every 100 to 500 ms,preferably every 300 ms, and the second frequency value is chosen suchthat the receiver of the slave device is activated every 0.5 to 30 s,preferably every 2 to 20 and most preferably about every 3 s. Further,the short and the long preamble periods utilized by the controller arepreferably chosen such that they exceed the time period of the “highfrequency” power saving mode and the “low frequency” power saving mode,respectively, by about 25 ms. Thus, in the most preferred embodiment,the preamble periods are approximately 325 ms and approximately 3025 ms,respectively. Further, it is preferred that the predetermined powersaving timeout period is 10 s to 60 s and preferably about 15 s. Thesevalues result in a good balance between low energy consumption and lowresponse time of the blood glucose system.

In a preferred embodiment, the system includes at least one furtherslave device, at least one of which comprises a blood glucose sensingmeans, wherein all slave devices comprise a receiver, a transmitter anda control means configured in the same way as the receiver, thetransmitter and the control means, respectively, of the slave devicecomprising an insulin dispensing means. The control means of thecontroller is further adapted to include an indication of a target slavedevice in each communication initiation data frame in order toindividually address the various slave devices. The control means of theslave devices is further adapted to maintain the receiver of the slavedevice active at least until the receiver has received the target deviceindication, and maintain the receiver of the slave device active untilthe remainder of the communication initiation data frame has beenreceived and switch the slave device into communication mode if theslave device is the target slave device, or, in case the slave device isnot the target device, maintain the slave device in the power savingmode, and set the receiver activation frequency for the slave device toa third frequency value, which is greater than the second frequencyvalue and is preferably identical to the first frequency value andsubsequently set the receiver activation frequency to the secondfrequency value if the receiver does not receive a communicationinitiation data frame for a predetermined timeout period, in case thecontrol means determines that the slave device receives the preamblesignal during a listening period.

It is further preferred that following transmission of a communicationinitiation data frame, the control means of the master controller isfurther operable to activate the transmitter of the controller for atleast one further transmission period to transmit at least one furtherdata frame addressed to or intended for the same slave device andincluding a preamble portion such that the preamble signal istransmitted for a preamble period, and following transmission of each ofthe least one further data frame to activate the receiver of thecontroller for a response period, which can e.g. be 50 ms to 500 ms andpreferably about 100 ms, wherein all data frames transmitted by thecontroller include a command portion in which a command is included. Thecontrol means of the controller is further adapted to include acommunication initiation command in the command portion of anycommunication initiation data frame to indicate that this data frame isa communication initiation data frame. The control means of the slavedevices is further adapted to determine whether the receiver of theslave device receives the preamble signal during a listening periodwhile it is in the power saving mode, and in case this determination ispositive to maintain the receiver of the slave device active until thecommand included in the command portion of the data frame has beenreceived, and maintain the slave device in the power saving mode in casethe command is not the communication initiation command. The controlmeans of the slave devices is further adapted to determine whether thereceiver of the slave device receives the preamble signal while it is inthe communication mode, and in case this determination is positive tomaintain the receiver of the slave device active at least until thecommand included in the command portion of the data frame has beenreceived, and if the command is not the communication initiation commandand the slave device is the intended recipient of the data frame,maintain the receiver of the slave device active until the remainder ofthe data frame has been received, and activate and deactivate thetransmitter of the slave device to transmit a response to thecontroller. It should be noted that each slave device transmits aresponse upon receipt of the communication initiation data frameinstructing this slave device to switch to communication mode, i.e. thecommunication initiation data frame starting a communication cycle, aswell as upon receipt of any further data frame addressed to this slavedevice and received by this slave device when it is still incommunication mode. Therefore, in each communication cycle with aparticular slave device, all data frames transmitted by the controllerto this slave device entail a response data frame transmitted by theslave device to the controller. Depending on the type of data frametransmitted by the controller, the response data frame may be a mereconfirmation of receipt or may include further data requested by thecontroller.

In a further preferred embodiment, the control means of each slavedevice is adapted to terminate the communication mode if the receiverdoes not receive a data frame for the respective slave device for apredetermined communication timeout period, and to maintain the receiverof the respective slave device active in communication mode whenever itdoes not activate the transmitter to transmit a response. In a preferredembodiment, the predetermined communication timeout period is 0.2 to 2.5s and preferably approximately 2 s.

It is also preferred that the controller further includes a timer, andthat the control means of the controller is adapted to start the timerupon transmitting a data frame to a particular slave device, todetermine, prior to transmitting a data frame to the same slave device,based on a comparison between the current value of the timer and thepredetermined communication timeout period whether the slave device isexpected to still be in communication mode, and in case it determinesthat the slave device is expected to still be in communication mode toinitially transmit the data frame such that the preamble period spans atime period shorter than the cycle durations corresponding to the firstfrequency value and the second frequency value.

It is further preferred that the control means of each slave device isadapted to include a delay time period indication into a responsetransmitted by the slave device to a particular first data frame toindicate that the actual response will be transmitted later, todeactivate the transmitter and the receiver for the indicated delay timeperiod, to activate the receiver of the slave device after the end ofthe delay time period to wait for the receipt of a second data framerequesting the response to the first data frame, and to subsequentlyactivate the transmitter of the slave device to transmit the requestedresponse to the controller, and that the control means of the controlleris adapted to deactivate, upon receipt of a response including a delaytime period indication, the transmitter and the receiver of thecontroller for the indicated delay time period, and to activate thetransmitter of the controller after the end of the delay time period totransmit a second data frame requesting the response to the first dataframe.

In a preferred embodiment, the control means of the controller isoperable to transmit a data frame including a termination command to aslave device in communication mode, and the control means of each slavedevice is adapted to terminate the communication mode upon receipt ofthis data frame. This possibility of terminating the communication modeof a slave device is preferably combined with the above describedembodiment in which the communication mode at a particular slave deviceis terminated if no communication initiation data frame or further dataframe addressed to this slave device is received for a predeterminedcommunication timeout period. It is then preferred that thecommunication mode should always be terminated by means of a terminationcommand, and that the communication timeout period is only provided as asafety feature to avoid that in case of errors a slave deviceinadvertently remains in communication mode permanently.

In a preferred embodiment, the controller comprises an actuation means,actuation of which provides a signal to the control means instructingthe control means to transmit a data frame.

It is also preferred that the controller further comprises a timer eventgenerator operable to periodically generate a timer event and to providecorresponding timer event signals to the control means of thecontroller, and that the control means of the controller is adapted totransmit a communication initiation data frame upon receipt of such atimer event signal. In this case, it is further preferred that thefrequency with which the timer event generator generates the timerevents has the second frequency value or is such that the secondfrequency value is an integral multiple of the timer event frequency,the controller comprises a clock and the control means of the controlleris adapted to include a time reference derived from the clock in eachdata frame initiated by the receipt of a timer event signal, and thecontrol means of the slave devices are adapted to examine the timereference upon receipt at a slave device, and to synchronize by means ofthe time reference the start times of the listening periods with thetimer events. Preferably, the timer event generator is able to generatesuch timer events every 3 to 5 min, preferably about every 5 min.

In a preferred embodiment, the controller includes a blood glucosesensing means. Thus, the system may include a separate blood glucosesensing device configured as slave and/or may include a controller intowhich a blood glucose sensing device is integrated.

In the following, the invention is explained in more detail for apreferred embodiment with reference to the figures.

FIG. 1 a shows a schematic representation of a blood glucose systemaccording to the present invention.

FIG. 1 b shows a schematic representation of a further blood glucosesystem according to the present invention.

FIG. 2 a shows a schematic block diagram of the main components of thecontroller forming part of a blood glucose system according to thepresent invention.

FIG. 2 b shows a schematic block diagram of the main components of aslave device forming part of a blood glucose system according to thepresent invention.

FIG. 3 a is a schematic flowchart diagram illustrating the controllerside of a preferred embodiment of the method in accordance with thepresent invention.

FIG. 3 b is a schematic flowchart diagram illustrating the slave side ofa preferred embodiment of the method in accordance with the presentinvention.

FIG. 4 is a schematic illustration of a data frame.

FIG. 5 a is a schematic flowchart diagram illustrating the slave side ofa delayed response mechanism.

FIG. 5 b is a schematic flowchart diagram illustrating the controllerside of the delayed response mechanism.

In FIG. 1 a, a blood glucose system 1 is schematically shown comprisinga controller 2, an insulin pump 3 for dispensing insulin to the bloodcircuit of a patient, and a blood glucose measuring device 4 fordetermining the level of blood glucose. The controller 2 includes ahousing 5, a display 6 and a number of control keys 7 which may beutilized to initiate a particular action by the controller 2 or to inputdata into the controller 2, e.g. in order to adjust the operation of theinsulin pump 3 with regard to various patient parameters such as e.g.his or her weight. Further main components of the controller 2 aredepicted in the schematic block diagram shown in FIG. 2 a. Accordingly,the controller 2 further comprises a battery 8, a transmitter 9, areceiver 10, an antenna 11 coupled to the transmitter 9 and the receiver10, and a clock 23. The operation of the controller 2 is controlled bycontrol electronics 12. In particular, the control electronics 12 areoperable to compose data frames to be transmitted by means of thetransmitter 9, to analyze data frames received by the receiver 10, andto activate and deactivate the transmitter 9 and the receiver 10 totransmit and receive, respectively, data frames. By means of the clock23, the control electronics 12 may provide timer functions (creating,starting and stopping timers) and to define and create timer events.

The insulin pump 3 and the blood glucose measuring device 4 eachcomprise a housing 13, a display 14 and an antenna 15. Further maincomponents of the insulin pump 3 and the measuring device 4 are depictedin the schematic block diagram shown in FIG. 2 b. Accordingly, theinsulin pump 3 and the measuring device 4 further comprise a battery 17,a transmitter 18 and a receiver 19 which are both coupled to the antenna15, and a clock 24. The operation of the controller 2 is controlled bycontrol electronics 21. In particular, the control electronics 21 areoperable to compose data frames to be transmitted by means of thetransmitter 18, to analyze data frames received by the receiver 19, andto activate and deactivate the transmitter 18 and the receiver 19 totransmit and receive, respectively, data frames. By means of the clock24, the control electronics 12 may provide timer functions (creating,starting and stopping timers) and to define and create timer events.Both devices also comprise a functional block 20. In the case of theinsulin pump 3, the block 20 is an insulin dispensing means, whereas inthe case of the blood glucose measuring device 4 the block 20 is aglucose sensing means that is able to analyze blood samples onenzyme-based test strips, that can be inserted into a test stripreceiving slot 16, in order to determine the blood glucose level basedon the enzymatic reaction. The controller 2 communicates with thedevices 3 and 4 via an RF air interface 22, which may e.g. use afrequency of 869.84 MHz for Europe or 903.02 MHz for the US and Canada,a binary separation of 64 kHz and FSK modulation. Manchester coding maybe utilized to allow for automatic balancing of the receivers and totest for Manchester violations. The data rate may e.g. be 9600 bps.

FIG. 1 b schematically shows an alternative blood glucose system V. Likethe system 1 of FIG. 1 a, the system 1′ comprises a controller 2′ and aninsulin pump 3 for dispensing insulin to the blood circuit of a patient.However, the system 1′ does not comprise a separate blood glucosemeasuring device 4. Rather, a blood glucose measuring means and a teststrip receiving slot 16′ are integrated into the controller 2′, i.e. thecontroller 2 and the blood glucose measuring device 4 of the system 1shown in FIG. 1 a are combined into a single device 2′ having a commonhousing 5.

In FIGS. 1 a and 1 b, the insulin pump 3 is illustrated as an externaldevice to be worn on the body of a patient. However, the insulin pump 3may also be constructed as an implantable device to be disposedsubcutaneously.

In the RF wireless network established by the controller 2, 2′ and thedevices 3 and 4, the controller 2, 2′ is configured as master and thedevices 3 and 4 are configured as slaves, i.e. they never initiate acommunication but only respond to commands received from the controller2, 2′. The controller 2, 2′ and the slave devices 3, 4 communicate byexchanging data frames, wherein each transmission preferably consists ofone data frame only. One such data frame 300 is shown schematically inFIG. 4. The data frame 300 comprises a preamble portion 301, an addressheader 302 (comprising a target address portion 303, a command portion304 and optional further header portions (not shown) such as a checksumportion, a source address portion and/or a frame number or framereference portion) and an optional data portion 305. The length of thepreamble portion 301 is variable to includes an adjustable number ofpreamble bytes having a characteristic bit pattern (e.g. 01010101), sothat upon transmission of the data frame a characteristic preamblesignal is transmitted for an adjustable period of time (preambleperiod). Each data frame 300 is addressed to a particular recipient. Inorder to indicate the intended recipient, the sender includes apredefined target device address into the target address portion 303.The type of data frame, i.e. command or response, and the type ofcommand are identified by a unique command or response identifierincluded in the command portion 304. Thus, upon receipt of a data frame300, the control electronics 12, 21 can determine whether the respectivedevice is the intended recipient. Further, it can be determined whichcommand or response the controller 2, 2′ or the devices 3, 4,respectively, have sent. Some commands may require further informationto be transmitted to the recipient. Such information may be includedinto the optional data portion 305. The same applies to additionalinformation, such as status data, transmitted as a response by thedevices 3, 4.

In FIGS. 3 a and 3 b, schematic diagrams of a preferred embodiment ofthe method according to the present invention is shown, wherein FIG. 3 ashows the steps performed in the controller 2, 2′ and FIG. 3 b shows thesteps performed in the insulin pump 3 and the blood glucose measuringdevice 4.

According to the embodiment shown in FIG. 3 b, the slave devices 3, 4normally operate in a power saving mode in which their transmitter 18and receiver 19 are usually deactivated and in which the receiver 19 isonly activated every 3 s for a listening period of 10 ms. Such a mode ofoperation is commonly termed sniff mode, and the interval between thestart times of successive listening periods is referred to as the sniffinterval. Thus, the operation of the slave devices 3, 4 starts in step200, in which the sniff interval is set to 3 s. After the sniff intervalhas elapsed (step 201), the receiver 19 is activated in step 202, and instep 203 it is determined whether a preamble signal can be detectedduring the listening period of 10 ms. If this is the case, the receiver19 is maintained active to receive the remainder of the data frame (step204). Subsequently, the command portion 304 of the received data frame300 is examined to determine whether it includes the communicationinitiation command identifier. This particular command is used by thecontroller 2, 2′ to switch the target device into a communication modein which the receiver 19 is activated essentially all the time.Accordingly, if it is determined in step 206 that the target addressportion 303 includes the address of the respective slave device, thereceiver is deactivated (step 207) and the slave device is switched tocommunication mode (step 208).

In communication mode, the transmitter 18 is activated and deactivatedto transmit a response to the controller 2, 2′ (step 209), and then thereceiver 19 is again activated (step 210) to wait for further dataframes 300 from the controller 2, 2′. The response to the communicationinitiation data frame indicates to the controller 2, 2′ that the slavedevice 3, 4 is now in communication mode. In contrast to the sniff mode,the receiver 19 is maintained activated until the preamble signal of afurther data frame 300 is detected or until a communication timeoutperiod of e.g. 2 s duration (i.e. longer than the listening period) haselapsed without detection of the preamble signal (step 211). If apreamble signal of a further data frame is detected in step 211, thefurther data frame is received in step 212. Otherwise, and in case noneof the received further data frames are addressed to the slave device,the slave device is switched back to power saving mode (step 214). Thesame happens if the command contained in the command portion 304 of thefurther data frame 300 indicates that the communication mode shall beterminated immediately (step 213). However, if the further data frame300 received in step 212 is not such a termination data frame, thereceiver 19 is deactivated in step 214 to go back to step 209 in orderto transmit a response. Depending on the command, such response may be amere confirmation of receipt or may include data requested by thecontroller 2, 2′. Thus, as long as the controller 2, 2′ continues totransmit further data frames 300 to the same slave device 3, 4 such thatthe preamble signals of the respective further data frames are receivedbefore the communication timeout period has elapsed, the slave device 3,4 stays in communication mode, in which the receiver 19 is onlydeactivated during the time it takes to transmit a response. In normaloperation, the communication mode is terminated by means of a furtherdata frame 300 including in the command portion 304 a terminationcommand.

Upon switching back from communication mode to power saving mode in step214, the sniff interval is adjusted to be 300 ms in order to reduce thedelay time in the case of a further communication attempt by thecontroller 2, 2′. The same is done in step 216, when a slave device 3, 4receives a data frame 300 including the communication initiation commandin the command portion 304, and determines in step 206 that the addresscontained in the address portion 303 is not its own address.

In any case, following receipt of a data frame 300 which is either not acommunication initiation data frame (step 205) or is a communicationinitiation data frame addressed to a different device (step 206), thereceiver 19 is deactivated for the rest of the sniff interval in step217. Subsequently, it is determined in step 218 whether the sniffinterval is currently 300 ms and whether a predetermined power savingtimeout period of e.g. 15 s has elapsed since the sniff interval waslast set to 300 ms. Before the end of this timeout period, the sniffinterval is left unchanged. If it has elapsed, the sniff interval ischanged to its normal value of 3 s in step 219. In this way, as soon asthe controller 2, 2′ initiates communication with one of its slavedevices 3, 4 the delay time is reduced for all of these devices 3, 4,thereby increasing the efficiency of communication in the blood glucosesystem 1, 1′ with its highly non-uniform traffic distribution on the airinterface.

With the slave devices 3, 4 operating in this manner, in casecommunication between the controller 2, 2′ and one of the devices 3, 4is desired, a data frame 300 is prepared in the controller 2, 2′ in step100 (FIG. 3 a). Prior to transmitting the data frame 300, the address ofthe target device is included into the target address portion 303 (step101), the identifier of the communication initiation command is includedinto the command portion 304 (step 102), and the number of preamblebytes is chosen such that the preamble period is 325 ms (step 103).Then, the transmitter 9 is activated and deactivated to transmit thisdata frame 300, and subsequently the receiver 10 is activated for aresponse period of 100 ms to wait for a response from the target slavedevice (e.g. confirmation of receipt). It is to be noted that the targetslave device 3, 4 will only definitely receive the data frame 300 if itssniff interval is currently 300 ms. In this case, the preamble periodchosen in step 103 spans the entire sniff interval. If, however, thesniff interval of the slave device 3, 4 is currently 3 s, the slavedevice 3, 4 will probably not detect the preamble signal within one ofits listening periods and will thus not send a response. Therefore, ifit is determined in step 106 that the slave device 3, 4 has nottransmitted a response, the number of preamble bytes in the preambleportion 301 of the data frame 300 is increase so as to adjust thepreamble period to 3025 ms, i.e. to a value spanning an entire 3 s sniffinterval. Then, the data frame 300 is retransmitted (step 108) and thereceiver 10 is activated for 100 ms to wait for a response.

After receipt of a response, it is ensured that the respective slavedevice 3, 4 is in communication mode with its receiver 19 activated. Inthis situation, a further data frame 300 is prepared (step 110), and instep 111 the address of the slave device 3, 4 is included in the addressportion 303, a suitable command is included in the command portion 304and optionally additional data are included in data portion 305. Thecontrol electronics 12 in combination with the clock 23 always track thetime since transmitting the last data frame to the current slave device,and in step 112 the control electronics 12 compare this time with thecommunication timeout period in order to determine whether the slavedevice is still in communication mode. If it is determined that thecurrent slave device 3, 4 is still in communication mode, the preambleperiod is set to 25 ms in step 114. This minimal preamble period issufficient since the target slave device is in communication mode sothat its receiver 19 is activated. However, it is necessary to transmitthe further data frames timely enough for the slave device to still bein communication mode, i.e. the time interval between successive dataframes must be smaller than the communication timeout period. Otherwise,if the above determination is negative, the controller goes back to step100 to initiate another communication cycle with the slave device (step113). Then, the further data frame 300 is transmitted in step 115,followed by activating the receiver 9 for 100 ms to wait for a response(step 116). Thus, the target slave has to respond within 100 ms ofreceipt of a data frame. If the controller 2, 2′ does not receive aresponse within this response time (step 117), it goes back to step 115in order to retransmit the further data frame. If it is determined thatfurther commands shall be transmitted to the same slave device (step118), another further data frame 300 is prepared in step 110. Otherwise,a data frame 300 including a termination command in its command portion304 is prepared and transmitted to the slave device in step 119 in orderto effect its switching back to power saving mode.

In certain cases, a slave device 3, 4, which just has received a furtherdata frame from the controller 2, 2′, may not be able to transmit aresponse within the response time period of the controller 2, 2′. Forexample, if the further data frame includes a command requesting theslave device 3, 4 to collect data and provide these data to thecontroller 2, 2′, the necessary data may not be available immediately.In such situations, the slave device 3, 4 has the possibility ofdelaying transmission of the response in step 209 and to perform thesteps of FIG. 5 a instead. Thus, in step 500 it is determined by meansof the control electronics 21 whether the data requested by thecontroller 2, 2′ are currently available. In the affirmative, the methodproceeds to step 209 (step 501). Otherwise, a data frame is transmittedthat includes a delay time period indication (step 502), and thereceiver 18 and the transmitter 19 of the slave device 3, 4 isdeactivated for the corresponding delay time period (step 503) in orderto save energy. After the delay time period has elapsed (as determinedby the control electronics 21 in combination with the clock 24), thereceiver 18 is activated in step 504 until a further data frameincluding a request to transmit the delayed response is received in step505. Then, the receiver is deactivated in step 506, and the methodproceeds to step 209 (step 507) in order to finally transmit theresponse to the original further data frame.

In order for this delay mechanism to work properly, the controller 2, 2′does not only determine whether a response has been received in step117, but the control electronics 12 further examine the receivedresponse to determine whether it includes a delay time indication (whichcould e.g. be represented by a suitable command and additional dataspecifying the delay time period). If no delay time indication is found,the method proceeds to step 118 (step 511). On the other hand, in case adelay time indication is found, the control electronics 12 effectdeactivation of the receiver 10 and the transmitter 9 for thecorresponding delay time period (step 512) in order to save energy.After the delay time period has elapsed (as determined by the controlelectronics 12 in combination with the clock 23), the controlelectronics 12 prepare a further data frame (step 513), include a targetdevice indication (step 514), and include a request command andadditional data requesting the target slave device to transmit aresponse to a particular earlier data frame (step 515). Then, thepreamble period is set to 25 ms in step 516 (which is sufficient becausethe target slave device has activated its receiver after the delay timeperiod has elapsed), and the request data frame is transmitted in step517. Finally, the method proceeds to step 116 (step 518) to wait for therequested response.

1. A method for wireless transmission of data between components of ablood glucose system including a master controller having a receiver anda transmitter and a slave device having a receiver and a transmitter,the method comprises the steps of: setting a preamble period to a firstpreamble period; transmitting a communication initiation data frame;activating a receiver of the master controller for a first receivingperiod of time to receive signals from the slave device; in the event noresponse has been received by the master controller during the firstreceiving period of time from the slave device then: setting thepreamble period to a second preamble period different from the firstperiod, retransmitting the communication initiation data frame, andactivating the receiver of the master controller for the first receivingperiod of time to receive signals from the slave device; in the event aresponse has been received by the master controller during the firstreceiving period of time then preparing further data frames to includethe slave device address portion and command portion, setting a preambleperiod to a second preamble period, transmitting the further dataframes, and activating the receiver of the master controller for thefirst receiving period of time to receive signals from the slave deviceuntil a response is received by the master controller.
 2. A method forwireless transmission of data between components of a blood glucosesystem including a master controller having a receiver and a transmitterand a slave device having a receiver and a transmitter, the methodcomprises the steps of: setting a sniff interval for the slave device toa first sniff interval; determining whether a preamble data transmissionis received within a first interval; in the event the determining stepis true, evaluating whether a remainder of the data frame is acommunication initiation data frame; in the event the evaluating step orthe determining step is false, deactivating the receiver of the slave orin the event the evaluating step is true, deciding whether an addressportion of the data frame includes an address of the slave device; andin the event the deciding step is true, deactivating the receiver of theslave device and switching the slave device to a communication mode. 3.A method for wireless transmission of data between components of a bloodglucose system including a master controller having a receiver and atransmitter and a slave device having a receiver and a transmitter, themethod comprises the steps of: setting a preamble period to a firstpreamble period; transmitting a communication initiation data frame;activating a receiver of the master controller for a first receivingperiod of time to receive signals from the slave device; in the event noresponse has been received by the master controller during the firstreceiving period of time from the slave device then: setting thepreamble period to a second preamble period different from the firstperiod, retransmitting the communication initiation data frame, andactivating the receiver of the master controller for the first receivingperiod of time to receive signals from the slave device; in the event aresponse has been received by the master controller during the firstreceiving period of time then preparing further data frames to includethe slave device address portion and command portion, setting a preambleperiod to a second preamble period, transmitting the further dataframes, and activating the receiver of the master controller for thefirst receiving period of time to receive signals from the slave deviceuntil a response is received by the master controller; setting a sniffinterval for the slave device to a first sniff interval; determiningwhether a preamble data transmission from the master controller isreceived within a first interval; in the event the determining step istrue, evaluating whether a remainder of the data frame includes acommunication initiation data frame; in the event the evaluating step orthe determining step is false then: deactivating the receiver of theslave and in the event the evaluating step is true, deciding whether anaddress portion of the data frame includes the address of the slavedevice; in the event the deciding step is true then: deactivating thereceiver of the slave device and switching the slave device to acommunication mode.
 4. The method of claim 1, further comprising thesteps of: setting a sniff interval for the slave device to a first sniffinterval; determining whether a preamble data transmission is receivedwithin a first interval (203); in the event the determining step istrue, evaluating whether a remainder of the data frame includes acommunication initiation data frame; in the event the evaluating step orthe determining step is false, deactivating the receiver of the slaveand in the event the evaluating step is true, deciding whether anaddress portion of the data frame includes the address of the slavedevice; and in the event the deciding step is true, deactivating thereceiver of the slave device and switching the slave device to acommunication mode.
 5. The method of one of claim 2, 3, or 5, in whichin the communication mode, the method comprises: transmitting a responsefrom the slave device to the master controller; and switching the slavedevice to a power saving mode from the communication mode; setting areceiver activation frequency to a first frequency upon the switchingstep and to a second frequency smaller than the first frequency if nocommunication data frame is received during a predetermined power savingtimeout period.
 6. The method of claim 5, in which the communicationinitiation data frame is transmitted in which the preamble period fortransmission of the data frame exceeds the length of the cycle durationcorresponding to the first frequency value.
 7. The method of claim 6, inwhich no response is received by the master controller during a responseperiod, retransmitting the communication initiation data frame in whichthe preamble period is increased and exceeds the length of the cycleduration corresponding to the second frequency value.
 8. The methodaccording to claim 7, further comprising at least another slave deviceincluding a blood glucose meter, in which the at least another slavedevice performs the same steps as the slave device in the form of aninfusion pump.
 9. The method according to claim 8, further comprisingtransmitting an indication of a target slave device in the communicationinitiation data frames by the controller in order to address eachcommunication initiation data frame to a particular slave device, and incase the particular slave device receives the preamble signalcorresponding to a communication initiation data frame during alistening period then: a) maintaining the receiver of the slave deviceactive at least until the target device indication has been received,and b) maintaining the receiver of the slave device active until theremainder of the communication initiation data frame has been receivedif the slave device is the target slave device, or, in case the slavedevice is not the target slave device then: maintaining the slave devicein the power saving mode and setting the activation frequency for theslave device to a third frequency value greater than the secondfrequency value and subsequently setting the activation frequency to thesecond frequency value if no communication initiation data frame isreceived for a predetermined timeout period.
 10. The method according toclaim 9, in which the third frequency value is identical to the firstfrequency value.
 11. The method according to claim 10, in which thecontroller only transmits communication initiation data frames.
 12. Themethod according to claim 10, further comprising the following steps:following transmission of a communication initiation data frame,activating the transmitter of the controller for at least one furthertransmission period to transmit at least one further data frameincluding a preamble portion which is chosen such that the preamblesignal is transmitted for a preamble period, and following transmissionof each of the at least one further data frame, activating the receiverof the controller for a response period, in which all data framestransmitted by the controller include a command portion in which acommand is included, including a communication initiation command in thecommand portion of any communication initiation data frame to indicatethat this data frame is a communication initiation data frame, or incase a slave device receives the preamble signal during a listeningperiod while it is in the power saving mode: a) maintaining the receiverof the slave device active at least until the command included in thecommand portion of the data frame has been received, and b) maintainingthe slave device in the power saving mode in case the command is not thecommunication initiation command, and in case a slave device receivesthe preamble signal while it is in the communication mode: a)maintaining the receiver of the slave device active at least until thecommand included in the command portion of the data frame has beenreceived, and b) if the command is not the communication initiationcommand and the slave device is the intended recipient of the dataframe, maintaining the receiver of the slave device active until theremainder of the data frame has been received, and activating anddeactivating the transmitter of the slave device to transmit a responseto the controller.
 13. The method according to claim 10, in which thecommunication mode is terminated if no data frame for the respectiveslave device is received for a predetermined communication timeoutperiod, and in which in communication mode the receiver of therespective slave device is maintained active whenever its transmitter isnot activated to transmit a response.
 14. The method according to claim13, further comprising the steps of tracking at the controller the timesince transmitting the last data frame to a particular slave device,determining at the controller, prior to transmitting a data frame to thesame slave device, based on a comparison between the tracked time andthe predetermined communication timeout period whether this slave deviceis expected to still be in communication mode, and, if it is determinedthat the slave device is expected to still be in communication mode,initially transmitting the data frame such that the preamble periodspans a time period shorter than the cycle durations corresponding tothe first frequency value and the second frequency value.
 15. The methodaccording to claim 14, further comprising the steps of: including adelay time period indication into a response transmitted by a slavedevice to a particular first data frame to indicate that the actualresponse will be transmitted later, deactivating the transmitter and thereceiver of both the slave device and the controller for the indicateddelay time period, activating the transmitter of the controller afterthe end of the delay time period to transmit a second data framerequesting the response to the first data frame, activating the receiverof the slave device after the end of the delay time period to wait forthe receipt of the second data frame, and subsequently activating thetransmitter of the slave device to transmit the requested response tothe controller.
 16. The method according to claim 10, in which a dataframe including a termination command is transmitted by means of thecontroller to a slave device in communication mode, and in which thecommunication mode of the slave device is terminated upon receipt ofthis data frame.
 17. The method according to claim 10, in which thetransmission of at least one communication initiation data frame by thecontroller is initiated by user request.
 18. The method according toclaim 10, further comprising the steps of periodically generating atimer event in the controller, and transmitting a communicationinitiation data frame by the controller upon each occurrence of a timerevent.
 19. The method according to claim 18, further comprising thesteps of: choosing the frequency at which the timer events occur to havethe second frequency value such that the second frequency valuecomprises an integral multiple of the timer event frequency, including atime reference in each communication initiation data frame initiated bya timer event, examining the time reference upon receipt at a slavedevice, and synchronizing by the time reference the start times of thelistening periods with the timer events.
 20. The method according to oneof claim 1, 2 or 3, in which the slave device comprises at least one ofan infusion pump and a blood glucose meter and in which the mastercontroller comprises at least one of an infusion pump and a bloodglucose meter.